Bcz ,embryosac has 3 antipodals ,2 synergies,1eggcell ,2 polarnuclei,so that's why it is 8 nucleated

Embryo sac, also known as the female gametophyte, is a crucial part of the reproductive system of angiosperms (flowering plants). It is formed within the ovule and plays a vital role in the process of fertilization, leading to the formation of seeds. A mature angiosperm embryo sac consists of a specific number of nuclei.

The correct answer to the question is option 'D', which indicates that a typical angiosperm embryo sac at maturity is 8-nucleate. This means that it contains eight nuclei. Let's understand this in detail.

The development of the angiosperm embryo sac can be divided into three main stages: megasporogenesis, megagametogenesis, and maturation.

1. Megasporogenesis:
During megasporogenesis, a single megasporocyte (diploid cell) in the ovule undergoes meiosis to produce four haploid megaspores. Three of these megaspores degenerate, while one survives.

2. Megagametogenesis:
The surviving megaspore undergoes several rounds of mitotic divisions, resulting in the formation of a seven-celled, eight-nucleate structure called the embryo sac. The megagametogenesis stage involves the following steps:

- The surviving megaspore undergoes three rounds of mitotic divisions without cytokinesis, resulting in the formation of eight nuclei within the embryo sac.
- The first mitotic division produces two nuclei, one at each end of the embryo sac. These nuclei are known as polar nuclei.
- The second mitotic division produces two nuclei at the micropylar (top) end of the embryo sac. These nuclei are known as synergids.
- The third mitotic division produces three nuclei at the chalazal (bottom) end of the embryo sac. Two of these nuclei are known as antipodal cells, and the third one is the egg cell or the female gamete.

3. Maturation:
During the maturation stage, the embryo sac undergoes some structural changes to prepare for fertilization. The synergids develop filiform apparatus, which helps in the guidance of the pollen tube during fertilization. The antipodal cells at the chalazal end often degenerate, leaving behind the mature embryo sac with eight nuclei.

In conclusion, a typical angiosperm embryo sac at maturity is 8-nucleate, consisting of one egg cell, two synergids, three antipodal cells (which may degenerate), and two polar nuclei. This structure is essential for sexual reproduction in flowering plants.